1. Field of the Invention
The present invention relates to a back-pressure valve for applying a back pressure to an actuator or the like.
2. Description of the Related Art
There is known a pressure accumulator having a relief valve as a conventional back-pressure valve. See, for example, Japanese Patent Publication No. JP-A-9-328098 (Page 7, FIG. 1).
In the conventional back-pressure valve, however, since there is generated a difference in hydraulic pressure between before and after the passage through the back-pressure valve, there has been caused a problem that hydraulic energy is lost.
Furthermore, in the conventional back-pressure valve, since a predetermined pressure for a relief valve is set larger than a desired predetermined pressure therefor to some extent in order to ensure the accumulation of the desired predetermined pressure, there has been caused a problem that the loss of hydraulic energy is increased.